Omron CP - PROGRAMMING MANUAL 05-2007 Programming Manual page 870

Serial Communications Instructions
Related Flags and Words
To ensure that RXDU(255) is not executed while the logical port is busy, pro-
gram the port's Communications Port Enabled Flag (A202.00 to A202.07) as
a normally open condition.
CPU Unit CJ-series Unit
RXDU
RXDU
Internal logic ports (8 ports)
RXDU(255) can not be executed while the Reception Completed Flag (bit 6 of
n+9 or n+19, where n = CIO 1500 + 25
Reception Completed Flag as a normally open condition of RXDU(255).
An error will occur and the Error Flag will turn ON in the following cases.
• The Communications Port Enabled Flag for the specified logical port is
OFF when RXDU(255) is executed.
• The value of C is not within range.
• The value for N is not between 0000 and 0100 hex.
Read the data using RXDU(255) as soon as possible after the Reception
Completed Flag turns ON. If reception is continued without reading the data,
the reception buffer (capacity: 260 bytes) will overflow and data reception will
stop. If this occurs, the port will have to be restarted to recover operation.
The reception buffer is cleared when RXDU(255) is executed for a serial port
on the Serial Communications Unit. Thus, more than one RXDU(255) instruc-
tion cannot be used to read the data.
The following words are related to RXDU(255) operation.
DM Setup Area Settings
(m = D30000 + 100 unit number)
Setup Area word Bit
Port 1 Port 2
m+4 m+14 8 to 15
0 to 7
m+5 m+15 12 to 15 No-protocol Mode Start
8 to 11
unit number) is ON. Program the
Name
No-protocol Mode Start
Code
No-protocol Mode End
Code
Code Specifier
No-protocol Mode End
Code Specifier
Section 3-23
Settings
00 to FF hex
00 to FF hex
0: None
1: Use start code.
0: None
1: Use end code.
2: Use CR+LF.
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